Polymer blends are both of fundamental scientific interest as well as commercial importance. The vast majority of polymers do not form blends, but phase-separate. The discovery of polymers that blend is considered a fortuitous event; particularly should they blend in all proportions. Since the cost, properties and processability of polymer blends are major considerations toward their commercialization, the discovery of blendable polymers is of considerable interest both to the polymer community as well as commercially. The addition of a polymer which is very expensive to an inexpensive polymer may not only enhance the properties and performance of the less expensive polymer, but has the potential to also lower the cost of the more expensive polymer if it can be blended with less expensive materials.
The majority of polymer pairs are immiscible and dispersion of one phase into the other leads to phase separation or otherwise tends to produce materials lacking useful properties. A limited number of polymer pairs are partially or fully miscible and the resulting blends may be homogeneous with useful properties, suggesting that polymer-polymer interactions on a molecular level have occurred and are directly related to the chemical structure of the repeat unit (Charrier, Polymeric Materials and Processing-Plastics, Composites and Elastomers, Munich: Hanser 1990). Harris, et al. have previously given many citations which confirm the fortuitous nature of finding polymers which are miscible and form blends (U.S. Pat. No. 4,879,354). BPA-PC blends with polymers other than polycarbonates are known which exhibit high mechanical strength, excellent ductility and thermal resistance, along with ease of processing. In these cases the polycarbonate was blended with styrenics, such as acylonitrile-butadiene-styrene (“ABS”) or acrylonitrile-styrene-acrylate (“ASA”), or with polyesters, such as polyethylene terephthalate (“PET”) or polybutylene terephthalate (“PBT”), but not with other polycarbonates.
That polycarbonate blends with aromatic polycarbonates are unusual as appreciated from the polymer literature. An early paper by Kim and Paul lists 9 homopolycarbonates which are NOT miscible with BPA-PC, and indicates specifically that “BPA-PC shows favorable interactions with other polycarbonates having a range of aliphatic connector groups including those having methyl groups on the phenyl rings.” (Kim and Paul, “Effects of Polycarbonate Molecular Structure on the Miscibility with Other Polymers”, Macromolecules 1992, 25:3097-3105). A tenth homopolycarbonate which is not miscible with BPA-PC is given in the more recent paper by Haggard and Paul (“Blends of high temperature copolycarbonates with bisphenol-A-polycarbonate and a copolyester”, Polymer 2004, 45:2313-2320). In addition to citing the immiscibility of the commercial isophorone-PC with BPA-PC, this paper also cites the facile miscibilities of many of the copolymers composed of the same monomers, in spite of the fact that the homopolymers are NOT miscible. In the same 1992 paper cited above, Kim and Paul conclude that “BPA-PC is miscible with a wide range of other polycarbonates having aliphatic hydrocarbon connector groups in the bisphenol. Incorporation of aromatic or strong polar connector groups seems to cause immiscibility with BPA-PC.”
Thus, miscibility of aromatic, especially high aspect ratio polycarbonates as in the present invention contradict previous findings in the literature in terms of what is known about miscibility. The present invention provides syntheses of numerous co- and homopolycarbonates containing high-aspect ratio bisphenolic monomers. Polycarbonate-containing aromatic monomers, such as bis[4-(4′-hydroxyphenyl)phenyl]propane (“TABPA”), or 2-(4-hydroxyphenyl)-2-[4-(4′-hydroxyphenyl)phenyl]propane (“TriBPA”), may be blended with miscibility with a variety of aromatic polycarbonate homopolymers and copolymers.